Which of the following is an anticoagulant rather than an antiplatelet medication?

• A. Aspirin
• B. Plavix
• C. Heparin
• D. Tissue plasminogen activator

Answer: (C)

Understanding the difference between anticoagulants, antiplatelets, and thrombolytics helps explain why this option fits best. Heparin is an anticoagulant because it enhances antithrombin III, which inhibits thrombin and factor Xa in the coagulation cascade, preventing formation and propagation of fibrin clots. Aspirin and Plavix are antiplatelet medications; aspirin inhibits COX-1 to reduce thromboxane A2 and platelet aggregation, while Plavix blocks the ADP receptor on platelets, both acting at the platelet activation step rather than the coagulation cascade. Tissue plasminogen activator is a thrombolytic, not an anticoagulant—it promotes conversion of plasminogen to plasmin to dissolve existing clots. So the anticoagulant in this list is heparin.